the Great Barrier Reef Lagoon have increased since 1823: Sediment - x 5.5 Nitrogen- x 5.7 Phosphorus - x 8.9 Kroon et al. 2012 Mitchell et al. 1997, 2001, Tilman et al. 2001, Smith et al. 2003, Devlin & Brodie 2005, Fabricius 2011
stay suspended and… Introduction Residence time of fine sediments, N and P: years to decades in the GBR lagoon All coral life history stages submitted to enriched sediments Kroon et al. 2012, Fabricius et al. 2013, Brodie et al. 2013
1.1 1.2 1.3 * Experiment 1: Effects of suspended sediments on recruit survivorship • Turbidity reduces energy for growth • Clearing sediments is energetically costly (mucus production: 2.5 x more expensive than other physiological functions; Riegl & Branch 1995) • Trade-off between growth and maintenance Recruits size
˂63 µm Incubation: 24 h Sedimentation: 1h approximately 4 enrichment levels Sample times: 3, 6, 12, 24, 48 h 5 vials Experiment 2: Effects of organically enriched sedimentation on recruit survivorship Survivorship: % recruits alive at each sample time and after 7 days of exposure Water sample analysis: Nitrogen, Phosphorus, Carbon, Pigments, Bacterial community (454 sequencing) Sediments Recruits 125 vials Control 0.1 OC% 0.3 OC% 0.9 OC%
and distribution are negatively impacted by: - suspended sediments - organically enriched sediments ü Benthic habitats exposed to excessive turbidity due to river run- off may be sub-optimal for corals.